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LCD TFT display important components introduction

Author:admin Time:2017-07-04

LCD TFT display, as we all know, there are many components, Europa League, this article will introduce you 7 LCD TFT important components, as well as some of their role and application.
Liquid crystal capacitor and storage capacitor
According to the structure of the TFT LCD screen, the two layer glass asked with liquid crystal, liquid crystal is the equivalent capacitance of capacitive material, commonly known as the liquid crystal capacitor CLC, its size is about 0.1pf, but the actual application, the capacitor will not maintain voltage to the next and then update the time picture data that is to say, when the TFT of the capacitor charge, it will not keep the voltage, until the next TFT to the point of charging time (in general 60Hz screen update frequency, need to keep about 16ms of the time, as a result, voltage) has changed, will be shown in gray is not correct, therefore, generally in the panel design, will add a storage capacitor C. (typically, the pixel electrode is formed with a common electrode), the capacity of which is about 0.5pf so that the charged voltage can be maintained until the next update.
3 head Apple press
The picture shows the 3 apple press in the European Union
Two, thin film transistors (TFT)
Thin film transistors, referred to as TFT devices, also known as TFT switches, are based on the principle of field effect transistors, that is to say, TFT devices are electric tubes that use electric field effects to control current. TFT is a unipolar device because there is only one kind of polar carrier involved in conducting. The TFT device also has 3 electrodes, that is, the source s (equivalent to the e pole of the triode), the gate g (equivalent to the B pole of the triode) and the drain D (equal to the C pole of the triode). But the control characteristics of the two is different, the transistor is a current control device, by controlling the base current to control the current collector or emitter current, namely the need to provide a current signal source to work, therefore, its input resistance is low; the TFT device is voltage controller output current depends on it the input voltage of the signal source, basically does not need to provide current, so its input impedance is very high. In addition, the TFT device also has the advantages of fast switching speed, high frequency characteristics, good thermal stability and low noise. TFT devices are mainly a-Si (amorphous silicon) and p-Si (polysilicon) two, of which p-Si (polysilicon) is in the initial stage of development, and a-Si is widely used. Figure 1-3 shows the schematic diagram and circuit symbols of the a-Si amorphous silicon TFT device.
TFT device, like a voltage controlled bidirectional switch, when the gate voltage is g, the TFT device in the off state (off state), which is the source and drain s D can not be connected, at the gate of G and S (the source or drain the resistance between D) called off the resistance of roff. Since the leakage current of the gate G is very small or not, the Roff is very high, generally more than 107 omega. When applying a G gate turn-on voltage is greater than the voltage, due to electric field device TFT (a) TFT device (b) TFT devices will sign in the conducting state, the source and drain on S D, the source and drain d s the resistance is called resistance Ron, it decreases with the increase of the gate voltage and. For the TFT device, the source s is the same as the drain D characteristic, and the function can be interchanged. The current direction between the source s and the drain D varies with the electric field direction between them. The source and drain are defined in the application circuit. Generally, the input signal end is called source s, and the output signal is called drain D. In the TFT LCD panel, the data driver is usually connected with the source s of the TFT device, and the pixel end is connected with the drain D of the TFT device.
Three pixel electrode and common electrode
The pixel electrodes are distributed on the back glass, and the common electrodes are distributed on the front glass, which together constitute the pixel unit. The pixel electrode, the common electrode, and the TFT device form a pixel unit (also called sub-pixel).
Four 、 row electrode and column electrode
From the drive mode, the TFT LCD screen connects all the row electrodes as scan lines to the gate driver and connects all the column electrodes as column signals to the source driver to form a drive array.
Five 、 alignment film
As we know, the two layers of glass (front and rear) of liquid crystal are used to clamp liquid crystals. The rear glass has a thin film transistor (TFT), and the former glass is stained with color filter. But the two pieces of glass are not smooth on the side of the liquid crystal, but have jagged grooves, as shown in figure 1-6. The main purpose of this groove is to arrange the linear liquid crystal molecules along the grooves, so that the arrangement of liquid crystal molecules will be neat. Because if it is a smooth plane, the arrangement of liquid crystal molecules will not neat, caused by light scattering, the formation of light leakage phenomenon. In the practical manufacturing process, and can be made of glass groove shaped distribution so, usually the first on the glass surface coated with a layer of PI (polyimide), and then cloth friction, so that the surface molecules of PI no longer stray distribution, in accordance with the fixed and uniform direction. And this layer Pi is called the alignment film, its function is like glass groove, provides the liquid crystal molecule to be arranged evenly the interface condition, lets the liquid crystal arrange according to the predetermined order.
Six, color filter
Strip arrangement is most often used in OA products, which are our laptops or desktop monitors. Why does this application come in strips? Because most of the software is now windowed, that is, what we see

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